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_ Jan. 7,v 1947. r
2,413,751
w. DENNIS
EXPANS ION ENGINE
Filed June 10, 1944
2 Sheets-Sheet lv
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Velma-x,
ATTQRNEYS
, Jan.,7, 1947. ,
'w. DENNIS
2,413,751
EXPANSION ENGINE
Filed June 10, 1944
2 ISheets-Sheet 2
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Wma»J”.AwNaCV;o aTm.”QM
Patented Jan. 7, ‘19.47
UNITED? srArE-s- PATENT OFFICE ‘
2,413,751
EXPANSION GINE
Wolcott Dennis, Darien, Conn., assignor to Air
‘Reduction Company, Incorporated, New York,
N. Y., a corporation of New York
Application June 10, 1944, Serial Nor-539,761
1
3 Claims.
I
(Cl- 121-1)
This invention ‘relates to expansion ‘engines
for liquefaction systems and particularly to im
cylinder 8 by bolts l4 extending through ?anges
I_ 5. The head provides inlet and exhaust passages
Hi and I1 terminating in valve seats l8 and I9 at
provements a?ording high e?lciency in the opera
tion of expansion engines at low temperatures.
In the liquefaction of gases by compression and
subsequent expansion as for example in the well
known Claude system, a part of the compressed
the upper end of section 8 of the cylinder. Valves
2!! and.2l are mounted to co-operate with the
valve seats and may be actuated by any suitable
mechanism (not shown) to open and close the
and cooled gas is expanded in an engine with ex
valves. Such mechanism will provide well known
ternal work. Although engines'have been em
means to regulate the lead and cut oil! of the
ployed in such systems for many years, little 10 valves in order that gas under pressure intro- ‘
improvement has been effected with respect to
the e?iciency of operation. It has been assumed
that certain undesirable losses in the operation
of the engine were unavoidable.
duced through the inlet l8 may be expanded in
the cylinder and discharged through the exhaust
'
It is the oblect of the present invention to pro ' 15
videvan engine adapted to afford a higher heat‘
drop-e?lciency than has been possible in engines
heretofore available for expansion of gases at
passage H. The details of- such mechanisms are
well known in the art and require no further de
scription.
~
'
Within the cylinder-6 a piston 22 is supported _
and provided with piston rings 23 hearing against
the internal surface of the cylinder 6 to prevent
low temperatures.
‘
' '
the escape or gas. A piston rod 24 is connected
Another object of the invention is to minimize 20 in any suitable manner, for example threadedly,
the losses due to the introduction of heat through
as indicated at 25, to a.‘ block 28 secured at the
friction between the moving parts.
_
end of the piston 22. The piston rod 24 may be
Another object of the invention is to provide
connected also to a conventional crosshead, crank,
for the maintenance of a temperature differential
and crankshaft (not shown) adapted to translate ‘
between the cold portion of ‘the cylinder ‘and 25 movement
of the piston. Preferably the piston is
the lubricated portion, by the action of the air
?lled with insulating material 21. A casing 28 is
or gas used to drive the engine.
disposed about the cylinder sections 6 and 8 and
A further ‘object of the invention is the provi
the
head l3‘ and is ?lled with insulating material
sion of a structure in which parts subject to wear
29 to reduce ?ow of heat from‘ the external at
can be replaced readily and economically so that 31 mosphere through the walls of the cylinder.
the enginecan be maintained at its original high
As indicated in the drawing, the lower end of
e?iciency and at relatively low cost.
the piston 22 has adiameter affording a rela
Other objects and advantages of the invention
tively close ?t with the cylinder 0. 'The upper end
will be apparent as it is better understood by ref
of the piston has a reduced diameter aifording a
erence to the following speci?cation and the
substantial clearance between the piston and the
accompanying drawings, in which
'
upper section 8 of the cylinder. The clearance
Fig. l is a vertical section illustrating one form
space is preferably tapered and extends beyond
of the invention; and
.
>
the limit of the stroke of the piston indicated by
Fig. 2 is a similar ‘view illustrating a modifi
the line :c—.r. The amount of radial clearance
cation of the engine.
40 between the upper end of the piston and the sec
Referring to the drawings, 5 indicates a suitable
tion 8 of the cylinder may vary. Preferably the ra- frame upon which a cylinder 6 is supported by
dial clearance at the top of the piston is approxi
bolts ‘i. The cylinder is in two sections, the
mately .010 inch and at the bottom of the reduced
upper section 8 being secured to the lower section
portion the radial clearance is approximately .005
6 by bolts 9 extending through the'?anges It and
inch.
However, the radial clearance may vary
H. ' A rabbeted joint i2 is provided between the
, from approximately .020 inch at the top of the
sections 6 and 8 of the cylinder to prevent escape
piston to .002 inch at the bottom of the reduced
of gas therethrough, and to insure accurate line
section.
v
up of the two sections. The construction of the
The
provision
of
an
unusually
large
clearance
cylinder in the form indicated permits the re
space between the upper portion of the piston
moval of the lower section 6 which is subjected
and the cylinder walls which are normally in
to wear and the replacement thereof at intervals
so that the engine can be maintained at its maxi
contact with the cold expanded gases, serves two i
useful purposes. First, all possibility of physical
contact
and the generation of heat by friction
A head 13 is secured ,to the upper end of the 65
in this portion of the cylinder is eliminated and
mum eiliciency.
‘
2,413,751
second, a heating effect is obtained in the lower
part of this space by the action of the gas being
diameter, affording clearance preferably though
used to operate the engine without in any way
not necessarily tapered, extending beyond the line
interfering with the attainment of high eiiiciency.
.’E——-.’l! representing the limit of travel of the pis
ton. The radial clearance between the piston
and the cylinder wall should be within the limits
hereinbefore speci?ed. The same advantages are
attained in this modi?cation, and further advan
tages resulting from the elimination of heat flow
from the warm end of the cylinder to the cold end
This heating effect results when gas is admitted
to the cylinder at the beginning of the working
stroke with a resulting compression of the resid
ual gas in the clearance space into the lower end
of this space. In being compressed this gas be
comes heated and transfers part of its heat of
compression to the cylinder and piston walls near
the bottom end of the clearance space.
as the result-of use of the insulating material at
the upper end of the piston and in the wall of the
On ex
pansion the gas in the clearance space cools but
the cooling effect on the walls at the bottom of
the space is much less than the previously noted
heating effect because the mass of gas in contact
upper section 33 of the cylinder.
structed in accordance with the principles set
forth has a heat drop efficiency of 88% under op
erating conditions such as exist in its application
to a Claude cycle.
Various changes may be made in the construc
tion and arrangement-of the apparatus within‘
the scope of the appended claims, without depart
ing from the invention or sacrificing the advan
tages thereof.
It is I
here utilized for the purpose of establishing a
large temperature gradient between the cold
parts of the cylinder and the working parts
which it is desirable to lubricate without difficul
I claim:
1. An expansion engine for gases at relatively
low temperatures comprising a cylinder, a cylin
der head associated therewith including inlet and
exhaust passages and valves controlling the deliv
ery of gases to and from the cylinder_ and a pis
ton movable in the cylinder and having a bear
ing surface closely ?tting the internal surface of
the cylinder at the end remote from the cylinder
head, the other end ‘of the piston having a re
duced diameter affording a relatively narrow ta
pered radial clearance between the piston and
cylinder walls, the maximum clearance being at
the cylinder-head end of the piston, the length of
ties due to freezing of oil or condensation of mois
ture. It is important of course that the cylin
der section 8 be made of such material and of
such thickness as to minimize heat conduction to
the lower cylinder section-B in order to realize the
most bene?t from the heating effect. It is also
desirableto extend the clearance space downward
so that when the piston is in its upper position
the space extends some distance below the lower
limit of the piston travel. With this construc
tion, the major portion of heat generated by com
that portion of the piston with reduced diameter
being greater than the stroke of the piston.
2. An expansion engine for gases at relatively
pression of residual gas in the clearance space is
transmitted to the cylinder 'wallsbelow the line
.r—-a:.
low temperatures comprising a cylinder, ‘a cylin
der head associated therewith including inlet and
exhaust passages andyvalves controlling the deliv
'
The use of a tapered piston permits the use of i
a larger clearance space at the top. for a given
clearance volume and reduces the possibility of
contact between piston and cylinder at the top
edge of the piston where contact is most apt to
occur.
.
It has been demonstrated that an engine con
with the previously heated walls is greatly re
duced by the expansion process.
This heating effect has been repeatedly‘ob
served in the connecting piping between engine
cylinders and indicator apparatus, and in engine
parts having a single outlet connected to the cyl
inder and subject to fluctuating pressure.
4
As in the preceding embodiment of the inven
tion, the upper section of the piston is of reduced
ery
ton
ing
the
.
Referring to Fig. 2, the frame 30 supports the
of gases to and from the cylinder, and a pis
movable in the cylinder and having a ‘bear
surface closely ?tting the internal surface of
cylinder at the end remote from the cylinder
head, the other end of the piston having a re
lower section 3| of the cylinder through bolts 32. ‘
duced diameter affording tapered radial clear
The upper section 33 of the cylinder is secured
to the lower section 3! by bolts 34 extending
through ?anges 35 and 3B. A rabbeted joint 31 is
provided as in the previous embodiment of the
ance between the piston and cylinder walls, said
clearance progressively decreasing from a maxi
mum of .020 inch at the cylinder-head end of the
piston to a minimum of .002 inch, the length of
invention. A head 38 is secured by bolts 39 to a
?ange 40 at the upper end of the ‘section 33 of the
Li
cylinder and provides inlet and exhaust passages
4| .and 42 terminating in valve seats 43 and 44.
Valves 45 and 46 are actuated by mechanism. as
in the preceding embodiment of the invention, to
control the ?ow of gas under pressure from the
inlet passage 4| and withdrawal of the expanded
gas through the exhaust passage 42.
that portion of the piston with reduced diameter
being greater than the stroke of the piston.
3. An expansion engine for gases at relatively
low temperatures comprising a cylinder, a cylin
der head associated therewith including inlet and
exhaust passages and valves controlling the deliv
ery of gases to and from the cylinder, and a pis
ton movable in the cylinder and having a bear
ing surface closely ?tting the internal surface of
the cylinder at the and remote from the cylinder
A piston 41 is supported in the cylinder and
provided with piston ‘rings 48 to afford a gas-tight
head, the other end of the piston having a re
l ?t. The piston is connected in the manner pre
viously described to a piston rod 49 which in turn
and crankshaft to translate movement of the pis
duced diameter affording tapered radial clear
ance between the piston and cylinder walls, said
clearance progressively decreasing from a maxi
mum of .010 inch at the cylinder-‘head end of the
ton.
piston to a minimum of .005 inch, the length of
is connected to a conventional crosshead. crank‘
The lower end of the piston has a substan
tially- tight lit in the section 3| of the cylinder.
The upper end of the piston consists of a block 50
of heat insulating material secured to the lower
portion by a bolt 5|. A liner 52 of heat insulat
ing material is disposed within the upper section
33 of the cylinder.
.
that portion of the piston with reduced diam
eter being greater than the stroke of the piston.
v
WOLCOT'I‘ DENNIS.‘
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